Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

net/mlx5e: Fix publication race for priv->channel_stats[]

mlx5e_channel_stats_alloc() publishes a new entry to priv->channel_stats[] and then increments priv->stats_nch as a publication token, but neither store carries any memory barrier:

priv->channel_stats[ix] = kvzalloc_node(...); if (!priv->channel_stats[ix]) return -ENOMEM; priv->stats_nch++;

Concurrent readers compute the loop bound from priv->stats_nch and then dereference priv->channel_stats[i] using plain accesses, e.g.

for (i = 0; i < priv->stats_nch; i++) { struct mlx5e_channel_stats *cs = priv->channel_stats[i]; ... cs->rq.packets ... }

On weakly-ordered architectures (ARM, PowerPC, RISC-V) the writes to channel_stats[ix] and stats_nch may become visible to other CPUs out of program order. A reader can observe stats_nch == N while still seeing channel_stats[N-1] == NULL, leading to a NULL pointer dereference in the channel_stats loop.

This has been observed in production on BlueField-3 DPUs (arm64), where ovs-vswitchd queries netdev statistics over netlink during NIC bringup, racing mlx5e_open_channel() -> mlx5e_channel_stats_alloc() on another CPU:

Unable to handle kernel NULL pointer dereference at virtual address 0x840 Hardware name: BlueField-3 DPU pc : mlx5e_fold_sw_stats64+0x30/0x180 [mlx5_core] Call trace: mlx5e_fold_sw_stats64+0x30/0x180 [mlx5_core] dev_get_stats+0x50/0xc0 ovs_vport_get_stats+0x38/0xac…